package main

// Go offers built-in support for regular expressions.

import (
	"bytes"
	"fmt"
	"regexp"
)

func main() {
	// This tests whether a pattern matches a string
	match, _ := regexp.MatchString("p([a-z]+)ch", "peach")
	fmt.Println(match)

	// Above we used a string pattern directly, but for other regexp
	// tasks you'll need to Compile an optimized Regexp struct
	r, _ := regexp.Compile("p([a-z]+)ch")

	// Many methods are available on these structs.
	fmt.Println(r.MatchString("peach"))

	// This finds the match for the regexp
	fmt.Println(r.FindString("peach punch"))

	// This also finds the first match but returns the start and end
	// indexes for the match instead of the matching text.
	fmt.Println(r.FindStringIndex("peach punch"))

	// The Submatch variants include information about both the whole-pattern
	// matches and the submatches within those matches. For example this
	// will return information for both p([a-z]+)ch and ([a-z]+)
	fmt.Println(r.FindStringSubmatch("peach punch"))

	// Similarly this will return information about the indexes of matches
	// and submatches
	fmt.Println(r.FindStringSubmatchIndex("peach punch"))

	// The All variants of these functions apply to all matches in the input
	// not just the first. For example to find all matches for a regexp
	fmt.Println(r.FindAllString("peach punch pinch", -1))

	// These All variants are available for the other functions we saw above
	// as well
	fmt.Println("all:", r.FindAllStringSubmatchIndex("peach punch pinch", -1))

	// Providing a non-negative integer as the second argument to these functions
	// will limit the number of matches.
	fmt.Println(r.FindAllString("peach punch pinch", 2))

	// Our examples above had string arguments and used names like MatchString.
	// We can also provide []byte arguments and drop String from the function name
	fmt.Println(r.Match([]byte("peach")))

	// When creating global variables with regular expressions you can use the
	// MustCompile variation of Compile. Mustcompile panics instead of returning
	// an error, which makes it safer to use for global variables.
	r = regexp.MustCompile("p([a-z]+)ch")
	fmt.Println("regexp: ", r)

	// The regexp package can also be used to replace subsets of strings with
	// other values
	fmt.Println(r.ReplaceAllString("a peach", "<fruit>"))

	// The Func variant allows you to transform matched text with a given function
	in := []byte("a peach")
	out := r.ReplaceAllFunc(in, bytes.ToUpper)
	fmt.Println(string(out))
}
